Experimental approaches to studying the fission process using the surrogate reaction technique

Over the past several years, Lawrence Livermore National Laboratory has been developing the surrogate technique to study the properties of fission and perform precision cross section measurements. The surrogate technique allows nuclear physicists to measure previously unattainable compound-nuclear cross sections of nuclei currently one to two nucleons away from a stable or long lived (∼ 10,000 y) nucleus. The goal of the surrogate technique is to create the same excited compound nucleus as is produced in a specific desired direct neutron reaction, study the decay channels and extract the cross section of choice; (n,γ), (n,2n) or (n,f). This may be accomplished via an inelastic scattering reaction (e.g. (p,p'), (d,d'), (3He,3He')), a neutron transfer reaction (e.g. (d,p), (18O,16O)), or a pick-up reaction such as (3He,4He). To measure the decay channels (gamma-ray or fission) we have constructed the Silicon Telescope Array for Reactions Studies (STARS), the Livermore Berkeley Array for Collaborative Experiments (LIBERACE) and the HYDRA array for precision fission studies. Preliminary results from a recent 238Pu(n,f) measurement are presented. (authors)